1. Field of the Invention
The present invention relates generally to a robotic system that is useful in nuclear power plants and other structures with a difficult to access geometry. More particularly, it relates to such a system which inserts a flexible lance into tube gaps of a steam generator, and similar difficult to access geometries. Most especially, it relates to such a system which is usable with difficult to access geometries having small access ports, known as hand holes in the case of steam generators for nuclear power plants.
In the system as disclosed in the Ruggieri et al. parent application, a flexible lance transporter having drive motors and positioning sensors mounted on the transporter is inserted through an access port known as a hand hole of a steam generator into a blow down lane, which runs down the center of a tube bundle in the steam generator. In order to accommodate the geometry of the transporter and a support rail for the transporter, it is necessary that the hand hole have a diameter which is about three times the height of the flexible lance driven through the flexible lance transporter. Thus, for a flexible lance having a height of two inches, a hand hole having a diameter of six inches is required with the system of the Ruggieri et al. parent application.
A substantial proportion of nuclear power plant steam generators have hand holes of sufficient diameter to accommodate the transporter and its support rail. The flexible lance system as described in the Ruggieri et al. parent application has proved to be of substantial benefit in such steam generators having large enough hand holes to accommodate the transporter and its support rail. However, many such steam generators lack large enough hand holes for this purpose. It would be desirable to provide the benefit of a flexible lance system in steamgenerators lacking such large hand holes as well.
2. Description of the Prior Art
Nuclear power generation equipment of the pressurized water reactor type consists of two major parts, the reactor and the steam generator. The steam generator includes a heat exchanger, which, in simple terms, consists of a bundle of thin wall tubes, which are tightly spaced and arranged in a matrix-like fashion. The spacing between the tubes is less than 0.5 inches, and the tube height extends to tens of feet. Hot reactor coolant is pumped through the tubes, which in turn heats water under pressure above the boiling point to several hundred degrees, thus generating steam.
In the operation of the steam generator, sludge deposits build up between the tubes. The steamgenerator needs to be cleaned periodically in order to remove these sludge deposits.